气相色谱法测定饮用水中二氯乙酸和三氯乙酸含量的不确定度评定

李晓晶; 林玉娜; 甘平胜; 杨荣; 曾涛; 刘苗; 罗晓燕; 潘心红

doi:10.13421/j.cnki.hjwsxzz.2022.10.009

气相色谱法测定饮用水中二氯乙酸和三氯乙酸含量的不确定度评定

Evaluation of uncertainty in measurement of dichloroacetic acid and trichloroacetic acid in drinking water by gas chromatography

摘要

摘要:
目的对气相色谱法测定饮用水中二氯乙酸和三氯乙酸含量的不确定度进行评定。
方法依据《测量不确定度评定与表示》（JJF 1059.1-2012）建立生活饮用水中二氯乙酸和三氯乙酸测定的数学模型，分析测定过程中各不确定度来源，评估饮用水中二氯乙酸和三氯乙酸含量测定的不确定度。
结果当饮用水中二氯乙酸和三氯乙酸含量为0.010 8和0.003 83 mg/L时，包含概率为95%，包含因子k=2，其扩展相对不确定的度分别为0.002 8和0.000 62 mg/L。
结论通过对不确定度的分析，发现标准曲线拟合残差是气相色谱法测定饮用水中二氯乙酸和三氯乙酸不确定度的主要来源，在测量时注意合理选择标准物质，准确配制标准溶液，做好标准曲线。

Abstract:
Objective To evaluate the uncertainty in measurement model of dichloroacetic acid and trichloroacetic acid in drinking water by gas chromatography.
Methods According to the Evaluation and Expression of Uncertainty in Measurement (JJF 1059.1-2012), a mathematical model was built to calculate the content of dichloroacetic acid and trichloroacetic acid in drinking water, and the sources and magnitudes of uncertainty in measurement were analyzed to evaluate the uncertainty in determining the content of dichloroacetic acid and trichloroacetic acid in drinking water.
Results When the content of dichloroacetic acid and trichloroacetic acid in drinking water was 0.010 8 and 0.003 83 mg/L, respectively, the relative extended standard uncertainties were 0.002 8 and 0.000 62 mg/L, respectively, at a confidence level of 95% and a coverage factor of 2.
Conclusion The curve fitting residual is the major source of uncertainty in gas chromatography-based measurement of dichloroacetic acid and trichloroacetic acid in drinking water.Rational selection of standard substance and accurate preparation of standard solution are key steps for a good standard curve.

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